Stick with the tried and true brand, like the anticipated iPhone 6? Go for a bigger display? Find a model that supports LTE-Advanced over LTE?

Smartphone makers spend millions of dollars on surveys and studies to anticipate what buyers want in a new device. Price and value always matter, but In the U.S., most high-end smartphones still cost $200 on a two-year contract or about $650 unlocked, with various installment plans available. That means cost in the high-end category is not always the big driver of customer choice. Elsewhere in the world, however, low-cost smartphones are in great demand, which may eventually affect prices for even high-quality smartphones in the U.S.

Computerworld asked four smartphone analysts to predict what design and features will matter the most to U.S. buyers of high-end smartphones this fall. There was general agreement that brand matters greatly, followed by the size of the display and resolution, body design, processor speed and battery life.

One survey of 20,000 potential U.S. customers by Kantar WorldWide in early 2014 found 4G/LTE capability was the biggest issue of importance to customers, followed by screen size. Acccording to some reports, the next iPhone, (probably called the iPhone 6) could be announced by Apple on Sept. 9 with a chip to support one version of LTE-Advanced. That chip could support theoretical download speeds of 150Mbps, more than triple today's theoretical download speed on ordinary U.S. LTE networks of 40Mbps. (Average speeds are much slower, in the 10Mbps range.)

One version of the Samsung Galaxy S5 offers LTE-Advanced connectivity, an important feature for some buyers.

One LTE-Advanced version of the Samsung Galaxy S5 is now available, but analysts said it hardly matters in the U.S., because carrier networks aren't expected to support LTE-Advanced for two years or more.

What's in a (brand) name?

It's fairly easy to see why a returning smartphone buyer would stick with the same brand, or at least the same OS: easy access to the same apps.

Apple and even Samsung buyers are loyal. "It takes something revolutionary that other phones don't have to get people to switch, like Siri when it was new," said Jack Gold, an analyst at J. Gold Associates. Nokia has been known for having the best cameras in the smartphone market, but that hasn't been enough to overcome the lack of interest in the Windows Phone platform, he said.

"Folks who buy high-end anything are typically status driven [and] start with things like a brand consistent with an elite image," said Rob Enderle, an analyst at Enderle Group.

Ken Dulaney, an analyst at Gartner, said smartphone buyers most want a strong ecosystem, which includes the hardware brand, but also a strong OS and a large number of apps. All those qualities apply to both Android, running on many phones from multiple manufacturers, and iOS on the iPhone.

For first-time smartphone buyers, Kantar's survey found an overwhelming influence from in-store clerks on customers to buy a Samsung phone. Most smartphones are purchased in-store, so demos there are big factor in purchases. Kantar's survey found that 59% of buyers who were recommended a Samsung phone in-store bought one, while just 6% bought an iPhone.

Display size and resolution

After brand, analysts and the Kantar survey found the display size and resolution are very important to buyers. "Bigger is better for most consumers," Kantar said in a research report, authored by Carolina Milanesi, chief of research.

The screen-size race among vendors actually started two years ago, and some smartphone displays are well over 5-in. diagonally. The coming Sony Xperia Z3 is expected to have a 5.2-in. display while the Moto G is expected to have a 5-in. display and the Samsung Galaxy Note 4 could have a 5.7-in. display.

Apple's iPhone 6 could be quite a bit smaller, at 4.7-in., although there are rumors a of second model at 5.5-in. "If there's only the 4.7-in., I think that customer interest would be more limited, unless the device had something very unique about it," she said. "4.9 to 5.5 is the sweet spot, while over 5.5 is still a niche."

One rumored feature of the next iPhone is a tough platinum display, something that could attract buyers but didn't register very high with Computerworld's surveyed analysts.

While there's expected to be a greater vendor focus this fall on screen clarity and resolution, those qualities might not especially be on the minds of many customers. Kantar's survey found clarity and screen resolution are less important than battery life, camera quality, overall durability and 4G/LTE capability into customers. (LTE was at the top of the list.)

"Today's phones have more than you need," Dulaney argued. "Do you really need a 4K screen?"

Longer battery life, faster processor

All four analysts listed longer battery life and faster processing as important, but less so than brand/ecosystem and display size. "Users have an expectation of all-day or better battery life and if the device doesn't meet that, it gets panned," Gold said.

It's getting harder to make predictions before a purchase of how long a battery will last when playing streaming video or other rich data, although some carriers and vendors offer a ballpark figure.

Processors are constantly improving and being incorporated in new phones. The coming Note 4 may have the Qualcomm Snapdragon 805, while the next iPhone could have a new A8 chip, faster than the A7 with 64-bit architecture that debuted in last year's iPhone 5S.

Some reports have suggested Apple could include 1GB of RAM in the A8 chip, the same amount as in the A6 processor in the iPhone 5. RAM constantly consumes power, and having less memory should improve battery life.

Gold said that if buyers simply look at processor size and speed in a purchase, they could be misled. What usually matters more is how well a phone performs, something not always processor-dependent since it involves many factors such as the software, apps and the browser. That overall performance quality is hard to assess from looking at a spec sheet before making a purchase.

"Do you need a faster processor when most of what you do is browsing?" Dulaney asked. Better yet, how important can a faster processor be if you mostly text or read emails on a phone?

Other factors that don't -- or shouldn't -- matter

Kantar's survey found that the color of the phone was the least important design feature considered, behind overall attractiveness, quality of materials and screen size.

The iPhone 5C's colors didn't give the device a big boost in sales.

In 2013, the gold iPhone 5S got a lot of press, while an array of iPhone 5C colors emerged. And Nokia's Lumia family includes some of the brightest colors available. "Despite the recent focus on color, consumers do not seem to put a high priority on that feature," Milanesi said in the Kantar survey. "You would think that color would help differentiate, [but] it is clear from the survey results that color is not a deciding factor."

The colorful smartphone fad might be seen as a way to differentiate a model from what Milanesi calls a "sea of black rectangular devices" -- even if color is ineffectual.

Dulaney added, "The days of innovating on smartphone form factor are over; they are all black rectangles. To that end, innovation moves to the semiconductor technology and screens and software."

Enderle said an unusual color can work to attract a customer -- as long as it gives a particular phone that elusive, "exclusive" quality.

Along with doubts about the value of color, Dulaney questioned why today's smartphone makers put so much emphasis on what software ships natively in the device or can be loaded from an app store. "In software, we may be entering the silly era where all this wizbang software is interesting for the high-end buyer, even though few use the features long term," he said. "There are so many things running on phones these days that the user never learns to use them."

Ultimately, many U.S. buyers will notice that there are features on smartphones that they don't need, like 128GB of storage when everything can be stored in the cloud, he said. In the future, such excessive features "won't hurt, and some people will buy, but the masses will move down the price curve toward the medium and lower-priced phones."

His prediction makes it sound like U.S. smartphone buyers within five years will resemble the cost-conscious buyers of China or India. But most analysts believe there will always be high-end smartphone buyers in the U.S. who line up outside the Apple stores by the thousands to get the latest, brand-spankin' new iPhone.